CHYTRIDIALES 359 



Scherffel noted that the parasites avoided the girdle-band face and 

 bored through the siliceous cell wall. 



PODOCHYTRIUM Pfitzer 



Sitzungsber. Niederrhein. Gesell. Natur- und Heilkunde, 1869: 62. 1870 



(Fig. 21 B-E; K-L, p. 360) 



Septocarpus Zopf, Nova Acta Acad. Leop. -Carol., 52: 348. 1888. 

 Rhizidiopsis Sparrow, Trans. Brit. Mycol. Soc, 18:216. 1933; J. Linn. 

 Soc. London (Bot.), 50: 450. 1936. 



Thallus epi- and endobiotic, monocentric, eucarpic, the epibiotic part 

 consisting of the unexpanded body of the encysted zoospore and an 

 apical prolongation, the endobiotic part rhizoidal or straplike, arising 

 from the tip of a needle-like penetration tube; sporangium inoperculate, 

 epibiotic, formed from the apical prolongation of the sterile epibiotic 

 cyst of the zoospore, from which it is usually separated by a cross wall; 

 zoospores posteriorly uniflagellate, with a single globule; resting spore 

 sessile, flattened, thick-walled, upon germination producing a sporan- 

 gium. 



Members of the genus are confined to diatoms, so far as now known. 



Sparrow and Paterson recently (1955) discussed the status of 

 Rhizidiopsis. Since the basal septum on the sporangium is so variable 

 in its occurrence, the chief point of distinction of Rhizidiopsis from 

 Podochytrium breaks down. 



KEY TO THE SPECIES OF PODOCHYTRIUM 



Endobiotic system composed of delicate, branched rhizoids 



Sporangium clavate P. clavatum, p. 361 



Sporangium lanceolate P. lanceolatum, p. 362 



Endobiotic system composed of coarse, straplike rhizoids 



Sporangium narrowly clavate, hornlike, 33-58 \x long; on Stephano- 



discus P. comutum, p. 362 



Sporangium more broadly clavate, 6-26 y. long; on Melosira 



P. emmanuelense, p. 363 



